Frequent flowering but low sexual reproductive success of the dioecious seagrass Enhalus acoroides in Li’an Bay, China

Abstract

Abstract Seagrasses are rapidly declining worldwide. To safeguard and restore their natural populations, it is fundamental to understand first the biological properties that influence seagrass ecological and demographic trends. Such characteristics are typically linked to the reproductive success of these flowering plants, modulating the genetic diversity and the adaptive potential of seagrass populations. Aiming to inform future restoration efforts, we investigated the reproductive phenology and fruit set of the dioecious tropical seagrass Enhalus acoroides in Li’an lagoon, Hainan Island, China. Although E. acoroides flowered year-round, the flowering intensity varied across seasons (highest in the summer and lowest in the winter), most likely mediated by sea surface temperatures and tides. Mature fruits occurred predominantly in fall and winter, but the frequency was low probably due to the influence of disturbance and algal blooms. Despite the high reproductive investment in terms of flower formation observed throughout the year in E. acoroides, there was limited sexual reproductive success evidenced by the low fruit formation. This study provides insight into the reproductive ecology of E. acoroides, which will be useful for the future conservation and restoration of this threatened seagrass.